Just for context: I'm trying to use rclone first time and cannot confirm anything except initial configuration works.
In Google drive ther is a section "Be aware that ... very scary confirmation screen...". I believe that scary scrren can be, and perhaps should be, avoided by adding your user to "Test users":
In Google APIs console with your app selected, select "OAuth consent screen" in left pane, scroll down in the right pane to "Test users", click "+ Add users". A dialog appears on right side - fill your google e-mail into the box and click on "SAVE" button.